Oxaceprol versus tramadol for knee osteoarthritis: A randomized controlled trial

To assess efficacy and safety of oxaceprol, a hydroxyproline derivative with putative mechanism of action different from traditional nonsteroidal anti-inflammatory drugs, in symptomatic knee osteoarthritis, in comparison to tramadol.

A parallel group, double-blind, randomized controlled trial was conducted with ambulatory patients over 50 years age suffering from knee osteoarthritis causing pain of at least moderate intensity. Patients were randomized to receive either oxaceprol 200 mg thrice daily or tramadol 50 mg thrice daily for 12 weeks. The primary efficacy variable was symptom relief as assessed by Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) version 3.1 for pain, stiffness, and physical function. Responder rate (50% pain relief), patient's Clinical Global Impression (CGI), and rescue medication use were other outcomes measured. Vital signs, routine blood counts, tests of hepatorenal function and treatment-emergent adverse events were recorded for safety assessment.

From 91 patients recruited, 43 on oxaceprol and 36 on tramadol were evaluable. The WOMAC scores declined significantly from baseline in each arm but remained comparable between groups throughout the 12-week study period. The CGI ratings and 50% responder rates were also comparable at the final visit. Differences in dose up-titration and rescue medication requirements were statistically nonsignificant. So also were the adverse event counts. Compliance was satisfactory in both groups.

Efficacy and tolerability of oxaceprol were comparable to tramadol, and the drug can be considered as an alternative to low-potency opioids in the management of knee osteoarthritis.